Measuring probe and measuring probe system

ABSTRACT

A measuring probe for measuring a screw groove of a relatively movable ball screw includes a light source, an objective lens formed to correspond to the screw groove of the ball screw, arranged to be opposed to the screw groove of the ball screw in a non-contact manner, and configured to emit light from the light source to the screw groove of the ball screw, and a line sensor configured to detect an interference pattern generated by reflected light from the screw groove of the ball screw and reflected light on a surface of the objective lens. This enables high-accuracy measurement of a specified area of a shape of a side surface of a relatively movable work in a non-contact manner.

CROSS-REFERENCE TO RELATED APPLICATION

The disclosure of Japanese Patent Application No. 2016-75420 filed onApr. 4, 2016 including specifications, drawings and claims isincorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a measuring probe and a measuring probesystem, and more specifically relates to a measuring probe and ameasuring probe system enabling high-accuracy measurement of a specifiedarea of a shape of a side surface of a relatively movable work in anon-contact manner.

BACKGROUND ART

Conventionally, a measuring probe described in JP 2010-2392 A is used.This measuring probe includes a contacting portion (stylus) to beinserted into a cam groove of a cylindrical cam. And the measuring probeis configured to measure a profile of the cylindrical cam, which is aside surface shape of a work, by making the stylus contact with upperand lower surfaces of the cam groove of the rotated cylindrical cam andmoving the stylus upward and downward.

SUMMARY OF THE INVENTION Technical Problem

However, since the stylus of the measuring probe described in JP2010-2392 A is in the contact type, only a contact point contacting thestylus is reflected on the profile. That is, the stylus measures thecontact “point” and cannot measure a shape of an “area.” Also, sincethis stylus has a configuration in which movement thereof has only to berestricted on the upper and lower surfaces of the cam groove, it isdifficult to clarify which of the upper and lower surfaces of the camgroove is reflected on the profile of the cylindrical cam.

The present invention has been made to solve the foregoing problems, andan object of the present invention is to provide a measuring probe and ameasuring probe system enabling high-accuracy measurement of a specifiedarea of a shape of a side surface of a relatively movable work in anon-contact manner.

Solution to Problem

The invention according to a first aspect of the present applicationsolved the above problems by providing a measuring probe for measuring aside surface shape of a relatively movable work, including a lightsource, an objective lens formed to correspond to the shape of the sidesurface of the work, arranged to be opposed to the side surface of thework in a non-contact manner, and configured to emit light from thelight source to the side surface of the work, and a sensor configured todetect an interference pattern generated by reflected light from theside surface of the work and reflected light on a surface of theobjective lens.

In the invention according to a second aspect of the presentapplication, the work is a rotating body and is rotatable relatively tothe measuring probe.

In the invention according to a third aspect of the present application,the work is a ball screw, the side surface shape is a screw groove, anda cross-sectional shape of the objective lens is a shape where arcs oftwo circles overlap with each other.

In the invention according to a fourth aspect of the presentapplication, the surface of the objective lens is formed in an arc alonga screw groove center portion of the screw groove in a planar view.

In the invention according to a fifth aspect of the present application,the sensor is a line sensor including a plurality of detection elementsonly in one line in a rotation shaft direction of the work.

In the invention according to a sixth aspect of the present application,the measuring probe further includes a collimator lens configured tocollimate light emitted from the light source, a beam splitterconfigured to reflect the collimated light passing through thecollimator lens to the side surface of the work, and an optical elementconfigured to condense the collimated light reflected on the beamsplitter to emit light from the light source vertically in a directiontowards the surface of the objective lens and the side surface of thework.

In the invention according to a seventh aspect of the presentapplication, the measuring probe further includes an isolator configuredto prevent reflection of light passing through both the collimator lensand the beam splitter, and light reflected on the sensor.

In the invention according to an eighth aspect of the presentapplication, the measuring probe further includes a sliding memberconfigured to contact the side surface of the work.

In the invention according to a ninth aspect of the present application,the sliding member has a pair of pieces, and the pieces are arranged tointerpose the objective lens therebetween.

In the invention according to a tenth aspect of the present application,a measuring probe system including the measuring probe according to anyone of the first to fourth aspects includes a signal processing deviceconfigured to analyze the interference pattern detected in the sensorand derive the shape of the side surface of the work.

According to the present invention, it is possible to measure aspecified area of a shape of a side surface of a relatively movable workin a non-contact manner with high accuracy.

These and other novel features and advantages of the present inventionwill become apparent from the following detailed description ofpreferred embodiments.

BRIEF DESCRIPTION OF DRAWINGS

The preferred embodiments will be described with reference to thedrawings, wherein like elements have been denoted throughout the figureswith like reference numerals, and wherein;

FIG. 1 is a schematic diagram illustrating an example of a measuringprobe system according to a first embodiment of the present invention;

FIG. 2A is a side view around a measuring probe in FIG. 1, and FIG. 2Bis an upper view around the measuring probe in FIG. 1;

FIG. 3A is a side view illustrating positional relationship between anobjective lens and a ball screw in FIGS. 2A and 2B, and FIG. 3B is afront view illustrating the positional relationship between theobjective lens and the ball screw in FIGS. 2A and 2B;

FIG. 4A is a schematic diagram illustrating relationship between aposition of a screw groove against the objective lens in FIGS. 2A and 2Band an interference pattern and illustrates a normal state, FIG. 4B is aschematic diagram illustrating relationship between the position of thescrew groove against the objective lens in FIGS. 2A and 2B and aninterference pattern and illustrates a state in which a diameter of thescrew groove has changed, and each of FIGS. 4C and 4D is a schematicdiagram illustrating relationship between the position of the screwgroove against the objective lens in FIGS. 2A and 2B and an interferencepattern and illustrates a state in which a lead pitch of the screwgroove has changed;

FIG. 5A illustrates shape errors of the screw groove and illustrates aGothic arch shape of the screw groove and contact points, FIG. 5Billustrates the shape errors of the screw groove and illustrates groovediameter irregularities, and FIG. 5C illustrates the shape errors of thescrew groove and illustrates lead irregularities;

FIG. 6A is a schematic diagram around a measuring probe according to asecond embodiment of the present invention, FIG. 6B is a schematicdiagram around a measuring probe according to a third embodiment of thepresent invention, and FIG. 6C is a schematic diagram around a measuringprobe according to a fourth embodiment of the present invention;

FIG. 7A is an upper view illustrating relationship between a tip end ofa measuring probe according to a fifth embodiment of the presentinvention and a ball screw, and each of FIGS. 7B and 7C is a side viewillustrating the relationship between the tip end of the measuring probeaccording to the fifth embodiment of the present invention and the ballscrew; and

FIG. 8 is a schematic diagram illustrating an example of a measuringprobe system according to a sixth embodiment of the present invention.

DESCRIPTION OF EMBODIMENT

Hereinbelow, an example of a first embodiment of the present inventionwill be described in detail with reference to FIGS. 1 to 5C.

First, an overview of a measuring probe system will be described.

A measuring probe system 100 includes a base 106, a rotation mechanism108, a measuring probe 124, a probe support mechanism 142, and a signalprocessing device 168, as illustrated in FIG. 1.

In the present embodiment, a work to be measured is a ball screw 102serving as a rotating body. The ball screw 102 is used to move a slideror the like (not illustrated) of a linear motion stage fixed to a nut NTvia balls BL with high accuracy, as illustrated in FIG. 5A, for example.A spiral screw groove 102A (rolling movement surface of the ball BL) atregular lead pitches is provided on a side surface of the ball screw102, as illustrated in FIGS. 3A and 5A (that is, a side surface shape ofthe work is the screw groove 102A). The cross-section of the screwgroove 102A is formed in a Gothic arch shape where arcs of two circlesCS (a cross-sectional shape of a screw groove upper surface 102B and across-sectional shape of a screw groove lower surface 102C) overlap witheach other to facilitate adjustment of a space between the screw groove102A and the ball BL, as illustrated in FIG. 5A, for example. The ballBL contacts the screw groove 102A at two contact points TP in totalconsisting of one contact point on the screw groove upper surface 102Band one contact point on the screw groove lower surface 102C. In theactual screw groove 102A, groove diameter irregularities EG occur oneach of these circles CS, as illustrated in FIG. 5B, when the screwgroove 102A is formed. Thus, the screw groove 102A causes correspondinglead irregularities EL (such as random walk of the contact point TP) tooccur, as illustrated in FIG. 5C. Accordingly, in the ball screw 102,not only shape errors of a base material thereof (an outer diametererror, an axial center error, a roundness error, and the like) but alsoshape errors of the screw groove 102A (a lead pitch error, a leadirregularity, and the like) occur correspondingly.

The base 106 is a base supporting the rotation mechanism 108 and theprobe support mechanism 142, as illustrated in FIG. 1. The base 106supports the ball screw 102 as well.

The rotation mechanism 108 is a mechanism configured to rotate the ballscrew 102, as illustrated in FIG. 1. The rotation mechanism 108 includesa column 110, a guide 112, a driving source (motor) 118, and a rotaryencoder 120. The column 110 is provided to erect on the base 106 andsupports the guide 112. The guide 112 supports one work support member114 to enable the work support member 114 to approach to and separatefrom the other work support member 114 arranged directly in the base106. The work support members 114 rotatably support the ball screw 102via a rotation shaft 104. That is, by moving the work support member 114supported to the guide 112, the two work support members 114 canrotatably support each of the ball screws 102 with various lengths.

As illustrated in FIG. 1, the rotation shaft 104 is detachably attachedto the ball screw 102 and is driven to be rotated via a timing belt 116by the driving source 118. Also, the rotation shaft 104 is directlyconnected to the rotary encoder 120 (the rotation shaft 104 may be fixedintegrally with the ball screw 102). The rotary encoder 120 is connectedto a display device 122. This enables a rotation angle of the ball screw102 to be confirmed on a display unit 122A of the display device 122.The driving source 118 and the display device 122 are connected to thesignal processing device 168.

The measuring probe 124 is arranged to be opposed to a side surface ofthe ball screw 102 and can measure the side surface shape (screw groove102A) of the ball screw 102 that can be rotated by the rotationmechanism 108, as illustrated in FIG. 1. The measuring probe 124 will bedescribed in detail below.

The probe support mechanism 142 is a mechanism configured to support themeasuring probe 124 to enable the measuring probe 124 to be opposed tothe side surface of the ball screw 102, as illustrated in FIG. 1. Theprobe support mechanism 142 includes an adjustment stage 144, a column146, a Z stage 148, a linear encoder 150, and a balance mechanism 158.The adjustment stage 144 is movable in an X direction on the base 106 toposition the measuring probe 124 with respect to the axial center O ofthe rotation shaft 104 (the adjustment stage 144 may be movable not onlyin the X direction but also in a Y direction perpendicular to the Xdirection). The column 146 is provided to erect on the adjustment stage144 and supports the Z stage 148. The Z stage 148 supports the measuringprobe 124 so as for the measuring probe 124 to be movable in a Zdirection. The linear encoder 150 is provided in the column 146.

As illustrated in FIG. 1, the linear encoder 150 includes a detectionhead 152 and a linear scale 154. The detection head 152 is fixed to themeasuring probe 124, and the linear scale 154 is fixed to the column146. The linear encoder 150 is connected to a display device 156. Thisenables a position of the measuring probe 124 in the Z direction to beconfirmed on a display unit 156A of the display device 156. Asillustrated in FIG. 1, the adjustment stage 144, the Z stage 148, andthe display device 156 are connected to the signal processing device168.

As illustrated in FIG. 1, the balance mechanism 158 is a mechanismconfigured to achieve movement of the measuring probe 124 with a smallforce. That is, the balance mechanism 158 enables the Z stage 148 tomove the measuring probe 124 with small torque. The balance mechanism158 includes a wire 160, two pulleys 162 and 164, and a balancer 166.The wire 160 connects the balancer 166, which is approximatelyequivalent in weight to the measuring probe 124, to the measuring probe124. The two pulleys 162 and 164 are rotatably fixed to the column 146and movably support the wire 160. However, such a balance mechanism isnot essential.

The signal processing device 168 is arranged outside the measuring probe124 and includes a storage unit (not illustrated) configured to storevarious initial values, and a processing unit 170 (FIG. 2A) configuredto read out the various initial values stored in the storage unit and toperform calculation, as illustrated in FIG. 1. Specifically, theprocessing unit 170 reads out design data of the ball screw 102 from thestorage unit and derives coordinates representing the shape of the screwgroove 102A. The processing unit 170 controls the driving source 118 androtates the ball screw 102 based on the derived coordinates. Theprocessing unit 170 also controls the probe support mechanism 142 andmoves the measuring probe 124 in the Z direction (and the X direction).The processing unit 170 correlates a rotation angle of the ball screw102 with a position of the measuring probe 124 in the Z direction andprocesses an output signal of the measuring probe 124. The signalprocessing device 168 is connected to input devices (not illustrated)such as a keyboard and a mouse, and the input devices enable input ofinstructions, setting of initial values, and selection and determinationof processing procedures in an appropriate manner.

Next, the measuring probe 124 will be described in detail mainly withreference to FIGS. 2A and 2B.

The measuring probe 124 includes a casing 126, a light source 128, acollimator lens 130, a beam splitter 132, a condensing lens 134, anobjective lens 136, an isolator 138, and a line sensor (sensor) 140, asillustrated in FIG. 2A. A not-illustrated light shielding structure isappropriately provided with the casing 126 to prevent stray light,scattering light, and the like from an outside and the light source 128from entering the line sensor 140. The casing 126 fixes the light source128, the collimator lens 130, the beam splitter 132, the condensing lens134, the objective lens 136, the isolator 138, and the line sensor 140.The light source 128 is a point-like light source such as amonochromatic LED. The wavelength of the light source 128 is preferablyas long as possible (e.g., infrared light) from a viewpoint of detectinga shape error in comparison with an ideal shape (design shape) of thescrew groove 102A, and this is not necessarily the case. The collimatorlens 130 is an optical element configured to collimate light emittedfrom the light source 128. The beam splitter 132 is an optical elementconfigured to reflect the collimated light passing through thecollimator lens 130 in a direction toward the axial center O of the ballscrew 102 (a direction of an optical axis P). The condensing lens 134 isan optical element configured to condense the collimated light reflectedon the beam splitter 132 to emit light R0 from the light source 128vertically to a surface 136A of the objective lens 136 providedsubsequently to the condensing lens 134 and a specified area of thescrew groove 102A.

The objective lens 136 is an approximately semi-circular cylindricallens, as illustrated in FIGS. 2A, 2B, 3A, and 3B. The objective lens 136is in a shape (design shape) corresponding to the screw groove 102A ofthe ball screw 102. That is, as illustrated in FIG. 3A, a lens uppersurface 136B and a lens lower surface 136C of the objective lens 136respectively correspond to the screw groove upper surface 102B and thescrew groove lower surface 102C, and a cross-sectional shape of thesurface 136A of the objective lens 136 is a shape where two arcs overlapwith each other. The objective lens 136 is arranged to be opposed to thescrew groove 102A in a non-contact manner (gap Gp) to enable the lightR0 from the light source 128 to be emitted to the screw groove 102A, asillustrated in FIG. 3A.

As illustrated in FIG. 3A, the light R0 from the light source 128 isperpendicular to the surface 136A of the objective lens 136. Thus, thelight R0 from the light source 128 is partially reflected on the surface136A of the objective lens 136 and follows the incident path of thelight R0 from the light source 128 in a reverse direction (reflectedlight R2). On the other hand, the light R0 from the light source 128that has not been reflected on the surface 136A of the objective lens136 is emitted vertically to the screw groove 102A. Thus, lightreflected on the screw groove 102A (reflected light R1) also follows theincident path of the light R0 from the light source 128 in a reversedirection. That is, the light path difference between the reflectedlight R1 and the reflected light R2 is twice the gap Gp between thescrew groove 102A and the surface 136A of the objective lens 136. Thegap Gp can be less than 10 μm, for example. The objective lens 136 maybe formed by means of molding, grinding, or polishing or directly by a3D printer.

As illustrated in FIG. 3B, the light R0 for measuring the screw groove102A is emitted to areas that the ball BL highly possibly contacts(measurement areas MAO) located between a screw groove center portion102D and a screw groove upper end portion 102E on the screw groove uppersurface 102B and between the screw groove center portion 102D and ascrew groove lower end portion 102F on the screw groove lower surface102C. The ball screw 102 is rotated against the measuring probe 124.Thus, by moving the measuring probe 124 in the Z direction along withrotation of the ball screw 102, the measuring probe 124 can continuouslymeasure strip-like areas (measurement target areas MA) along leads ofthe screw groove 102A. Also, as illustrated in FIG. 2B, while the entireshape of the objective lens 136 is the approximately semi-circularshape, the surface 136A is formed to some extent in an arc along thescrew groove center portion 102D in a planar view to an XY plane. Thus,a slightly wide-range area of the screw groove 102A in the Y directioncan be a measurement target of the measuring probe 124.

The isolator 138 prevents reflection of light passing through both thecollimator lens 130 and the beam splitter 132, and light reflected onthe line sensor 140 to prevent ghost on the line sensor 140 and adecrease of an S/N ratio of an interference pattern, as illustrated inFIG. 2A.

The line sensor 140 detects an interference pattern generated by thereflected light R1 on the screw groove 102A passing through both theobjective lens 136 and the beam splitter 132, and the reflected light R2on the surface 136A of the objective lens 136, as illustrated in FIG.2A. In the present embodiment, the line sensor 140 separately includes aline sensor 140A configured to measure a shape (posture) of the screwgroove lower surface 102C and a line sensor 140B configured to measure ashape (posture) of the screw groove upper surface 102B. However, onlyone line sensor may be used to measure the shapes of the screw grooveupper surface 102B and the screw groove lower surface 102C. The linesensor 140 includes a plurality of detection elements only in one linein a rotation shaft direction (direction of the axial center O of therotation shaft 104) of the ball screw 102. Pixels of the detectionelements are extremely narrow in the Z direction and extremely wide inthe Y direction. Accordingly, the line sensor 140 can detect theinterference pattern with a high contrast.

FIGS. 4A to 4D illustrate states of interference patterns detected bythe line sensors 140A and 140B in a case in which positionalrelationship between the objective lens 136 and the screw groove 102Ahas changed.

As illustrated in FIG. 4A, in a case in which the shape of the screwgroove 102A is equal to the design shape, the gap Gp between the screwgroove 102A and the surface 136A of the objective lens 136 is constantat the measurement areas MAO. Thus, the interference pattern stripes areat regular intervals in the measurement areas MAO.

Conversely, as illustrated in FIG. 4B, in a case in which the diameterof the screw groove 102A deviates from the design shape (for example, ina case in which the diameter is large as illustrated by thehollow-centered arrow), the gap Gp between the screw groove 102A and thesurface 136A of the objective lens 136 is not constant but changes inthe measurement areas MAO. Thus, the interference pattern stripes are atirregular intervals in the measurement areas MAO. It is to be noted thatthe hollow-centered arrows on the lower stage in FIG. 4B representexpansion and contraction of the intervals of the interference patternstripes.

Also, as illustrated in FIG. 4C, in a case in which a lead pitch of thescrew groove 102A is shorter than the design shape, as illustrated bythe hollow-centered arrow, the gap Gp between the screw groove uppersurface 102B and the lens upper surface 136B of the objective lens 136decreases while the gap Gp between the screw groove lower surface 102Cand the lens lower surface 136C of the objective lens 136 increases.Thus, the interference pattern on the line sensor 140A moves to thelower side of the drawing sheet, and the phase changes. At the sametime, the interference pattern on the line sensor 140B moves to theupper side of the drawing sheet, and the phase changes. It is to benoted that the hollow-centered arrows on the lower stage in FIG. 4Crepresent moving directions of the interference patterns.

Also, as illustrated in FIG. 4D, in a case in which a lead pitch of thescrew groove 102A is longer than the design shape, as illustrated by thehollow-centered arrow, the gap Gp between the screw groove upper surface102B and the lens upper surface 136B of the objective lens 136 increaseswhile the gap Gp between the screw groove lower surface 102C and thelens lower surface 136C of the objective lens 136 decreases. Thus, theinterference pattern on the line sensor 140A moves to the upper side ofthe drawing sheet, and the phase changes. At the same time, theinterference pattern on the line sensor 140B moves to the lower side ofthe drawing sheet, and the phase changes. It is to be noted that thehollow-centered arrows on the lower stage in FIG. 4D represent movingdirections of the interference patterns.

Meanwhile, as illustrated in FIG. 1, the measuring probe 124 isconnected to the signal processing device 168. That is, the signalprocessing device 168 can analyze the interference pattern detected inthe line sensor 140 and derive the shape of the screw groove 102A.

Next, a procedure for measuring the screw groove 102A performed by themeasuring probe 124 will be described.

First, the ball screw 102 as a target to be measured is attached to thework support member 114 so as for the ball screw 102 to be rotatablearound the rotation shaft 104. At this time, adjustment is performed sothat the axial center O of the rotation shaft 104 may be equal to theaxial center of the ball screw 102. Subsequently, with use of the probesupport mechanism 142, the height of the measuring probe 124 is adjustedto the height of a measurement start position of the ball screw 102, andadjustment is performed so that the optical axis P of the measuringprobe 124 may intersect with the axial center O. The angle of the ballscrew 102 is then adjusted with use of the rotation mechanism 108 sothat the screw groove 102A may be located on the optical axis P of themeasuring probe 124. Positional adjustment of the measuring probe 124 inthe X direction is then performed with use of the adjustment stage 144of the probe support mechanism 142 so that the objective lens 136 of themeasuring probe 124 and the screw groove 102A may have an appropriategap Gp therebetween.

Subsequently, by means of an instruction from an input device (notillustrated), a measuring program for the screw groove 102A is startedin the signal processing device 168. Thus, at the same time as the ballscrew 102 is rotated at predetermined speed, the height of the measuringprobe 124 is changed. The objective lens 136 of the measuring probe 124is set in a state of being opposed to the screw groove 102A at alltimes. Detection signals are output in real time from the measuringprobe 124, and the output signals are processed in the signal processingdevice 168. Meanwhile, this processing may be performed at the same timeas the control or after the end of the control.

Measurement of the ball screw 102 is terminated by the end of themeasuring program or an instruction from the input device.

In this manner, in the present embodiment, the objective lens 136 isformed to correspond to the screw groove 102A, is arranged to be opposedto the screw groove 102A in a non-contact manner, and emits the light R0from the light source 128 to the screw groove 102A. The line sensor 140then detects the interference pattern of the reflected light R1 from thescrew groove 102A and the reflected light R2 from the surface 136A ofthe objective lens 136. That is, the present embodiment employs aconfiguration in which the line sensor 140 detects the interferencepattern generated by a light path difference based on the gap Gp betweenthe objective lens 136 and the screw groove 102A. Accordingly, byprocessing an output of the line sensor 140 in the signal processingdevice 168, the measurement target area MA of the screw groove 102A forthe objective lens 136 to which the light R0 from the light source 128is emitted can be specified, and a shape of the measurement target areaMA can be measured.

Also, in the present embodiment, the screw groove 102A can be measuredin a non-contact manner. Thus, the shape of the measurement target area(specified area) MA including not only a relatively projected “point” inthe screw groove 102A but also a recessed area around the point can bemeasured. Also, since the measuring probe 124 is not configured to moveby contacting the ball screw 102, movement of the measuring probe 124does not depend on the actual lead pitch of the screw groove 102A. Thus,in the present embodiment, changes in diameter of the ball screw 102,changes in lead pitch, and the like as illustrated in FIGS. 4B to 4D canbe measured. That is, shape errors of the screw groove 102A of the ballscrew 102 (a lead pitch error, a lead irregularity, and the like) can bemeasured.

Also, in the present embodiment, the objective lens 136 can measure bothshapes of the screw groove upper surface 102B and the screw groove lowersurface 102C of the screw groove 102A at the same time. Thus, positionaladjustment of the objective lens 136 against the screw groove 102A iseasy, and measurement can be highly accurate. Also, since both theshapes of the screw groove upper surface 102B and the screw groove lowersurface 102C can be compared and examined at the same time, features offorming of the screw groove 102A can be found easily. Further,measurement can be performed more promptly than in a case of measuringthe screw groove upper surface 102B and the screw groove lower surface102C separately. Meanwhile, the present invention is not limited to thisand may employ a configuration of the objective lens in which onlyeither the screw groove upper surface or the screw groove lower surfaceof the screw groove is measured.

Also, in the present embodiment, using the line sensor 140 can shortentime per scan further than using an area sensor and can improve theresolution. Thus, time required for measurement can drastically beshortened with high resolution. Meanwhile, the present invention is notlimited to this and may use an area sensor without using the line sensoror may move a single detection element so as for the detection elementto work instead of the line sensor.

Also, in the present embodiment, the signal processing device 168arranged outside the measuring probe 124 processes the output of theline sensor 140 and derives the shape of the screw groove 102A. Thus,the measuring probe 124 itself can be reduced in size and weight. Sincethis signal processing device 168 also controls the entire system,efficiency of components involved with processing can be improved.Meanwhile, the present invention is not limited to this, and acalculation part for analyzing the interference pattern detected in theline sensor and deriving the shape of the screw groove may beincorporated into the measuring probe.

That is, in the present embodiment, it is possible to measure aspecified area (measurement target area MA) of the relatively movablescrew groove 102A in a non-contact manner with high accuracy.

Although the present invention has been described, taking the firstembodiment as an example, the present invention is not limited to theabove embodiment. That is, it is to be understood that the presentinvention can be altered and modified in design without departing fromthe scope of the present invention.

For example, although the isolator 138 is used in the measuring probe124 in the first embodiment, the present invention is not limited tothis. For example, a second embodiment illustrated in FIG. 6A may beemployed. Since the second embodiment has a configuration of the firstembodiment from which the isolator has been eliminated, the first digitsof the reference signs are just changed, and detailed description of thesecond embodiment will be omitted. Accordingly, in the presentembodiment, a measuring probe 224 can be reduced in size, weight, andcost further than in the first embodiment.

Alternatively, a third embodiment illustrated in FIG. 6B may beemployed. Since the third embodiment has a configuration of the firstembodiment including a condensing lens 337 and a reference lens 338instead of the isolator 138, the first digits of the reference signs arejust changed, and description of the third embodiment except thecondensing lens 337 and the reference lens 338 will basically beomitted.

As illustrated in FIG. 6B, the condensing lens 337 has an equal shape tothat of a condensing lens 334, and is arranged to have an equal lightpath length to that of the condensing lens 334 for light from a lightsource 328 passing through a beam splitter 332. Also, the reference lens338 has an equal shape to that of an objective lens 336, and is arrangedto have an equal light path length to that of the objective lens 336 forlight from the light source 328 passing through both the beam splitter332 and the condensing lens 337. That is, by arranging the condensinglens 337 and the reference lens 338, the amount of light having an equallight path length to that of the reflected light from the surface of theobjective lens 336 is increased, which causes a high contrast of theinterference pattern generated by the reflected light from the surfaceof the objective lens 336 to be achieved. Thus, the interference patterncan be detected at the line sensor 340 with a higher contrast than inthe above embodiments. That is, the shape of a screw groove 302A can bemeasured more accurately than in the above embodiments.

Also, although, in the second embodiment, an incident angle of light toan objective lens 236 is defined by a condensing lens 234, the presentinvention is not limited to this. For example, a fourth embodimentillustrated in FIG. 6C may be employed. Since the fourth embodiment hasa configuration of the second embodiment including a diffraction grating434 instead of the condensing lens 234, the first digits of thereference signs are just changed, and description of the fourthembodiment except the diffraction grating 434 will basically be omitted.

As illustrated in FIG. 6C, the diffraction grating 434 is formed in aflat plate shape and is a double diffraction grating, for example. Thus,in the present embodiment, positional adjustment of the diffractiongrating 434 is easier than that in the case of using the condensinglens, and a measuring probe 424 can be reduced in size and weight.

Also, although, in the above embodiments, movement of the measuringprobe in the Z direction is driven and controlled by the Z stage, thepresent invention is not limited to this. For example, a fifthembodiment illustrated in FIGS. 7A to 7C may be employed. Since thefifth embodiment differs from the above embodiments just in terms of aconfiguration of a tip end of the measuring probe, the first digits ofthe reference signs are just changed, and description of the fifthembodiment except the configuration of the tip end of the measuringprobe will basically be omitted.

In the present embodiment, a Z stage (not illustrated) just works as amovement guide of the measuring probe. At the tip end of the measuringprobe, a pair of ball bearings (sliding members) 526A is fixed in acasing (not illustrated) with an objective lens 536 interposedtherebetween. Each of the ball bearings 526A as a pair contacts an endportion of a screw groove 502A (for example, a screw groove upper endportion 502E in FIG. 7B or the screw groove upper end portion 502E and ascrew groove lower end portion 502F in FIG. 7C) (that is, the measuringprobe includes the pair of ball bearings 526A contacting the screwgroove 502A). Thus, rotation of a ball screw 502 causes movement of thescrew groove 502A in the Z direction, which causes movement of themeasuring probe in the Z direction. Accordingly, in the presentembodiment, since the Z stage dispenses with a driving source, andcontrol thereof is not required, the system itself can be reduced incost.

Also, although, in the above embodiments, the work is the ball screw,the present invention is not limited to this. For example, a sixthembodiment illustrated in FIG. 8 may be employed. Since the sixthembodiment differs from the first embodiment just in terms of a work,the first digits of the reference signs are just changed, anddescription of the sixth embodiment except a configuration relating tothe work will basically be omitted.

In the present embodiment, the work is a cylindrical cam 602, forexample. In the present embodiment, the cylindrical cam 602 is formed ina cylindrical shape and is provided on a side surface thereof with a camgroove having an approximately V-shaped cross-section (may be anapproximately trapezoidal cross-section). The objective lens is formedto correspond to the cam groove, is arranged to be opposed to the camgroove in a non-contact manner, and can emit light from the light sourceto (upper and lower surfaces of) the cam groove. Thus, in the presentembodiment, the shape(s) of (the upper and lower surfaces of) the camgroove can be measured.

Alternatively, the work may not be a rotating body but be a flat bodyprovided with an approximately V-shaped groove on an equal plane, andthe flat body may be movable relatively to the measuring probe.

Also, although, in the above embodiments, the work is rotated againstthe measuring probe by the rotation mechanism, the present invention isnot limited to this. The work may be fixed, and the measuring probe maybe rotated around the work. In any case, the work has only to berotatable relatively to the measuring probe.

Also, although, in the above embodiments, the measuring probe isconstituted by optical elements such as the beam splitter, thecollimator lens, and the condensing lens, the present invention is notlimited to this. These optical elements can be changed or omitted asneeded.

The present invention can widely be applied to a measuring probe formeasuring a shape of a side surface of a relatively movable work.

It should be apparent to those skilled in the art that theabove-described embodiments are merely illustrative which represent theapplication of the principles of the present invention. Numerous andvaried other arrangements can be readily devised by those skilled in theart without departing from the spirit and the scope of the presentinvention.

What is claimed is:
 1. A measuring probe for measuring a side surfaceshape of a relatively movable work, comprising: a light source; anobjective lens formed to correspond to the shape of the side surface ofthe work, arranged to be opposed to the side surface of the work in anon-contact manner, and configured to emit light from the light sourceto the side surface of the work; and a sensor configured to detect aninterference pattern generated by reflected light from the side surfaceof the work and reflected light on a surface of the objective lens. 2.The measuring probe according to claim 1, wherein the work is a rotatingbody and is rotatable relatively to the measuring probe.
 3. Themeasuring probe according to claim 2, wherein the work is a ball screw,and the side surface shape is a screw groove, and wherein across-sectional shape of the objective lens is a shape where arcs of twocircles overlap with each other.
 4. The measuring probe according toclaim 3, wherein the surface of the objective lens is formed in an arcalong a screw groove center portion of the screw groove in a planarview.
 5. The measuring probe according to claim 2, wherein the sensor isa line sensor including a plurality of detection elements only in oneline in a rotation shaft direction of the work.
 6. The measuring probeaccording to claim 1, further comprising: a collimator lens configuredto collimate light emitted from the light source; a beam splitterconfigured to reflect the collimated light passing through thecollimator lens in a direction towards the side surface of the work; andan optical element configured to condense the collimated light reflectedon the beam splitter to emit light from the light source vertically tothe surface of the objective lens and the side surface of the work. 7.The measuring probe according to claim 6, further comprising an isolatorconfigured to prevent reflection of light passing through both thecollimator lens and the beam splitter, and light reflected on thesensor.
 8. The measuring probe according to claim 1, further comprisinga sliding member configured to contact the side surface of the work. 9.The measuring probe according to claim 1, wherein the sliding member hasa pair of pieces, and the pieces are arranged to interpose the objectivelens therebetween.
 10. A measuring probe system including the measuringprobe according to claim 1, comprising: a signal processing deviceconfigured to analyze the interference pattern detected in the sensorand derive the shape of the side surface of the work.